All satellites require fuel for their rocket engines and thrusters. Typical propellant systems use hydrazine (N.sub.2 H.sub.4 ) and blends of hydrazine. Hydrazine and hydrazine blends are hazardous materials because of their corrosive, caustic, explosive and toxic properties. Special care must be taken in transportation and handling of these propellant fuels. Special procedures are also required by government agencies.
Propellant fuels must be loaded on board a satellite prior to launch. Hydrazine, for example, is generally transported to a launch site in standard fifty-five gallon drums. In vapor state, hydrazine can auto-decompose from catalytic effects or electric spark at such a rapid rate as to cause an explosion. Hydrazine is toxic and is easily ingested or absorbed through the skin. The National Institute for Occupational Safety and Health (NIOSH) recommends extreme caution in handling hydrazine to reduce the risk of cancer induced by exposure to hydrazine. The NIOSH proposed standards state that work place air concentrations should be controlled so that employees are not exposed to concentrations greater than 0.04 mg/m.sup.3 (0.03 ppm) during any 15-minute sample period. Additional information on hydrazine can be found in "Studies of Evaporation of Hydrazine and Procedures for Cleanup of Small Spills" , U.S. Department of Commerce, AD-A064 675.
The hazardous properties of hydrazine require special certification of containers and transportation modes as well as special handling. Spills are considered hazardous events and the potential of spills during handling of hydrazine requires special handling procedures. During handling operations where spills are possible, personnel are required to wear self-contained atmospheric pressurized environment (SCAPE) suits. All non-essential personnel must be removed from areas where there is a potential for exposure to hydrazine.
Traditional satellite fueling operations have been done using a fueling cart, 55 gallon drums of hydrazine, tanks of liquid Nitrogen (LN.sub.2), tanks of Helium or gaseous Nitrogen (GN.sub.2), isopropyl alcohol and waste tanks. Approximately six people wearing SCAPE suits are required for between four and eight hours for the fueling of a satellite. Traditional setup and fueling procedures for a satellite are complex and dangerous.
Those of skill in the art are aware that there are many disadvantages and difficulties associated with these traditional satellite fueling operations. These disadvantages include a higher probability of spills because SCAPE suits must be worn for much of the fueling operation. Due to the bulky nature of these suits, all operations which involve them are inefficient and increase the likelihood that an inadvertent spill would happen due to bumping equipment, for example. In addition, SCAPE suits are very expensive and significantly increase the cost of satellite fueling operations.
Another disadvantage to traditional satellite fueling operations is that there is no way to remove residual fuel from connections which are made between the satellite and the fuel cart. Residual fuel is a serious health and environmental hazard. As a result, drips of hydrazine must be contained and disposed.
Another disadvantage to traditional satellite fueling operations is that the fuel (usually hydrazine or a hydrazine blend) is transported from a supplier in a 55 gallon drum. The 55 gallon drums are bulky and difficult to work with increasing the risk of spills. The drums are opened at the launch site and fuel vapors are released into the atmosphere. Atmospheric exposure increases the risk of potential contamination of the fuel. Fuel that becomes contaminated can no longer be used and must be discarded. Discarding fuel requires special procedures because the fuel is a hazardous material.
Another disadvantage to traditional satellite fueling operations is that the amount of fuel in a 55 gallon drum is typically in excess of what a satellite requires. To deliver the proper amount of fuel, traditional satellite fueling operations typically require weighing the fuel at the fueling site. The weighing process is time consuming and increases the risk of improperly filling the satellite fuel tank because of potential human error. A 55 gallon drum cannot be emptied completely and the excess fuel must be discarded. Another problem with the use of 55 gallon drums is that the United States Department of Transportation (DOT) has recently forbid the transportation of hydrazine in 55 gallon drums.
Another disadvantage to traditional satellite fueling operations is that a typical fueling cart requires attaching a 55 gallon fuel drum, a waste drum, an isopropyl alcohol drum, waste vapor vents and Helium or gaseous Nitrogen (GN.sub.2) bottles. It also requires multiple attachments to the satellite. Each of these connections represents an opportunity for spills and exposure. Furthermore, each connection is time consuming. Launch facilities must have waste vapor vents capable of handling hydrazine or provide a hazardous vapor scrubber.
Another disadvantage to traditional satellite fueling operations is that the fueling carts are complex resulting in a low mean time between failures (MTBF). As a result of a low MTBF, spare parts are stocked and special training is required for personnel at the fueling site for repair of the fueling cart. In addition, the complex operation of traditional fueling carts does not allow non-specialist technicians to perform the fueling operations. The need for specially trained personnel significantly increases the cost of traditional satellite fueling operations. Another disadvantage is that a traditional fueling cart requires electricity to power vacuum pumps and control systems. The use of electricity significantly increases the risk of sparks and explosions.
As can be seen, traditional satellite fueling operations are dangerous, time consuming and expensive, and require disposal of significant hazardous waste. With traditional satellite fueling operations, only one satellite is typically prepared for launch. However, when many satellites are launched on a single platform, traditional fueling approaches are too time consuming and expensive. Traditional approaches are also impractical when many satellites need to be launched on a regular basis.
Thus what is needed are a method and apparatus that fuel satellites in a safe, quick and cost efficient manner while reducing the amount of hazardous waste. What is also needed are a method and apparatus for fueling satellites that are totally self-sufficient and require no external utilities. What is also needed are a method and apparatus for fueling satellites that do not require personnel to wear SCAPE suits. What is also needed are a method and apparatus for fueling satellites that remove residual fuel from the connections to a satellite without exposing the residual fuel to the atmosphere. What is also needed are a method and apparatus for fueling satellites that eliminate the use of 55 gallon drums, prevent fuel waste and contamination of the fuel so that no fuel needs to be disposed.
What is also needed are a method and apparatus for fueling satellites that do not require weighing the fuel at the launch site and eliminate the waste drum, the isopropyl alcohol drum and waste vapor vents. Thus what is also needed are a method and apparatus that reduce the number of connections made during satellite fueling operations and eliminate the requirement that the launch facilities have waste vapor vents or a hazardous vapor scrubber capable of handling hydrazine.